Web feeding system



Dec. 31, 1963 F. B. ROBERTS I 3,116,032

WEB FEEDING SYSTEM Filed June 28, 1961 92 JNVENTOA F-RANKL IN E. ROBERTS BY Afm-f-fzme lLtmmvve s United States Patent O 3,116,032 WEB FEEDHNG SYSTEM Franklin B. Roberts, Springfield, Mass., assigner to Package Machinery Ccmpany, East Longmeadow, Mass., a corporation of Massachusetts Filed fune 23, 1961, Ser. No. 120,340 7 Claims. (Cl. 242-7543) The present invention relates to improvements in feeding webs of sheet material drawn from `a supply roll.

The use of polyethylene films as a packaging or wrapping material Lhas caused substantial problems .in registering printed panels relative to 4the products being packaged or wrapped. With prior sheet materials, registration of printed panels had reached a very high standard of accuracy which has been difficult, and many times impossible, to match when using polyethylene and other similar films. The reason for these registration problems is due primarily to the ease with which polyethylene is stretched. If stretched beyond its yield point, the printed panels bercome too long. If stretched to any substantial degree below its yield point, the panels may shrink after tension is removed, so as to cause faulty registration.

This problem is increased by the fact that the paper feeds for many packaging and wrapping machines are either intermittent or must be shut down fairly frequently, which results in a non-uniform tension on the web and a lack of any uniformity or predictability in the amount of stretch which will occur. Further complicating the situation is the need for using larger diameter supply rolls of the film in order to accommodate increased rates of machine operation. The inertia of the larger rolls increases the stretch induced in a web as it is drawn from the roll and the roll accelerated.

The general object of the invention is to minimize, if not elim-inate, the problems which result from stretching of a web as it is fed from a supply roll.

Another object of the invention is to control rotation of a supply roll of sheet material in such a manner that a web intermittently dnawn therefrom is at all times maintained in a controlled path and never tensioned beyond its yield point and thus never permanently stretched.

A further object of the invention is to feed a web under a minimum, substantially constant tension so that panels printed thereon may be accurately registered on products being wrapped or pack-aged.

The invention is characterized by a rotatably mounted supply roll of sheet material, means for advancing a web drawn therefrom, and loop forming means therebetween.

The loop forming means comprise a pair of slackener rolls each movable to form separate loops of varying length. One slackener exerts a weaker force on the web than the other. The brake means `are energized whenever the loop around the weaker slackener exceeds a given minimum. Preferably the slackener exerting the stronger force on the web is controlled by constant force spring means which limit the pull on the web to a force approximating, but less than, what would permanently stretch on the web.

The means for advancing the web may preferably comprise a first intermittently operated pair of feed rolls and a second pair of feed rolls. A loop is formed around a slackener roll between the two pairs of feed rolls. The first pair of feed rolls advance the web at a faster rate than the second pair. Means -are provided for controlling operation of the first pair of feed rolls to maintain the length of the loop around the slackener within given limits. Prefenably, the slackener is of -a minimum weight sufficient lto properly track the web, so that the web, as it is advanced by the second pair of feed rolls is under a minimum substantially uniform tension.

llz Patented Dec. 31, 1963 ICC The -above and other related objects and features of the invention will be apparent from a reading of the following description of the disclosure found in the accompanying drawing and the novelty thereof pointed out in the Kappended claims.

In the drawing:

FIG. 1 is a perspective view rdiagrammatically showing a feed system embodying the present invention; and

FIG. 2 is a view of a simplified electrical circuit employed herein.

In FIG. l the various parts have been diagrammatically shown for the sake of simplicity and clarity since they are individually known in 4the prior `art but not, however, in the present combination.

A supply roll 10 of polyethylene or like film is mounted on a suitably journaled shaft 12. An electromagnetic brake 11 is provided to stop rotation of the supply roll 10 during operation of the apparatus as is later described. A web W is drawn from the supply roll 10 and trained about suitably journaled, fixed rolls 14 and 16. The web W next passes around a first slackener roll 18. The roll 18 is journaled at each end in a block 20 which is guided for vertical sliding movement between rails 22. The web W is next looped overa second slackener roll 24 which 4is rotatably mounted at each end in a block 26. The blocks 26 are slidably mounted between rails 28 for vertical reciprocation of the roll 24.

The web W is trained around a suitably journaled, fixed roll 30 and then is caught between a pair of feed rolls 32, 34. The feed rolls 32, 34B are suitably journaled and are interconnected by a pair of gears 36 for rotation at the same rate at all times. The rolls 32, 34 are of the same diameter so that the web W will be fed without any slippage as sufficient pressure is provided against the web. A sprocket 3S is secured to the shaft for roll 34 and a chain 40 is trained therearound. The chain 4@ is driven by a sprocket 42 secured to the output shaft of an electromagnetic clutch 44. The clutch 44. is driven by a chain 46 trained around a sprocket 48 which is secured to the shaft of a motor Si). The feed rolls 32, 34 are driven whenever the clutch 44 is energized. The clutch 44 also comprises a spring loaded brake which automatically prevents rotation of sprocket 42 and feed rolls 32, 34 when the clutch 44 is de-energized.

After passing from the feed rolls 32, 34, the web W is looped around rotatable, fixed rolls 52, S4 and a third slackener roll 56. The slackener roll S6 is mounted in the same fashion as the other slackener rolls with blocks 58 being guided for sliding movement between rails 69.

If desired, pinions may be secured to each end of the shafts for the slackener rolls 18, 24 and 56. These pinions would mesh with fixed racks to prevent the slackener rolls from cooking as they ride up and down. Such a use of racks and pinions is well known and not shown herein.

From the roll 54, the web W extends between a second pair of feed rolls 57, 58. The rolls S7, 58 are suitably journaled and have the same diameter and are connected by gears 61 for rotation at the same rate. A sprocket 62 is secured to the shaft for roll 58. A chain 64 is trained around the sprocket 62 and around a sprocket 66 also secured to the shaft of motor Sil.

The first slackener roll 18 is preferably urged downward by spring means attached to the blocks 2t). Preferably the spring means take the form of constant force springs 68 of the type disclosed in U.S. Patent No. 2,609,192. It is also preferable to attach constant force springs 70 to the blocks 26 to urge the second slackener roll 24 upwardly.

The circuit diagram of FIG. 2 is limited to those portions of the machine circuit which are pertinent to the present inventive concepts and also has been simplified for purposes of clarity and ease of description. Lines 72, '74 are connected across a source of electrical current. A circuit is completed through a limit switch 'Je to actuate the motor 5t). Other motor controls, including the onoli switch, have been omitted. The switch 76 is mounted n one of the rails 2d and is opened when the slackener roll 24 reaches a given upper height. The circuit through the brake lll is completed through a switch 75l which is opened when the slackener roll 24; reaches a given lower position.

The circuit for energizing the clutch lll-'5.- includes switches 30, 82 which are connected in series with the coil of a relay 34. The contacts 3d of relay 43 provide a hold-in circuit by-passing switch S2 once it has been momentarily closed. Physically, the switches Si), 32 are mounted to detect the lower and upper positions respectively of the slackener roll 516.

In operation, the feed rolls 57, 5% rotate continuously and at a constant rate so long as the switch '76 is closed (presuming the other controls therefor are properly energized). The feed roll clutch ld is energized so long as switch 8@ and either switch S2 or contacts 36 are closed. With clutch de energized, the web will be advanced by the first feed rolls 32, 3d at a slightly faster rate than it is being advanced by the rolls 57, 5h. This results in the length of loop around slackener roll 56 increasing so that the slackener 56 will be lowered until switch Si) is contactevd and opened, tius cle-energizing switch Clutch 44 will now be de-energized and rotation of the rolls 32, 34 stopped. The web will continue to be advanced by rolls 57, 58 causing the slackener 56 torise, first permitting the switch Sil to close and then closing switch 82 when the slackener 56 reaches its upper limit. The clutch 44 is energized and the web again advanced by the rolls 32, 34.

The web is therefore intermittently drawn from the supply roll lt). When the rolls 32, 3d irst advance the web (with the rolls in the position of FIG. l), the brake 11 will be energized and the slackener Z6 will be lowered as the web is drawn from the loop therearound. The slackener roll 18 remains stationary inasmuch as the force which it exerts on the web is substantially greater than the pull exerted by the slackener roll 2o. Vhen the slackener roll 26 engages stops defining its lower position, the switch 78 is opened and brake ll cie-energized. The supply roll is accelerated as the slackener roll i3 rises. Preferably the slackener roll .l is made as light as possible to minimize its inertia and then the springs 68 are provided to obtain a force on the web which approximates but is insuliicient to impart a permanent stretch to the web. That is, the yield point of the web is not exceeded. This force depends upon the width and thickness of the web and upon the grade and type of polyethylene which can readily be determined by simple experimentation or, in most cases, routine calculations. Thus the maximum permissible force is exerted on the web to accelerate the supply roll without permanently stretching the web.

The force of springs 7@ is just slightly greater than what is needed to counterbalance the weight of roll 24. The forces and proportions may be so calculated that the roll i8 will ascend as inertia continues rotation of the supply roll lit until an upper limit is reached whereupon the roll 2d will move upwardly. The brake lll will be energized and further ascent of the slackener 24 halted before the switch 76 is opened. The slackener 24 will rise sumciently to open switch 76 only when the web W is broken or the supply roll l@ exhausted.

The force of slackener roll Se is the minimum necessary to obtain proper tracking of the web. It will be noted that the brake elements of clutch fli4l prevent reverse rotation of the rolls 32, 34 so that the web W can at no time be retracted by slackener roll ld which exerts a greater pull on the web W than slaclrener 56.

The loop around slackener roll 56 is always under a minimum constant tension so that there will be a minimum constant stretch in the web advanced by the feed rolls 57, the web itself will not have been permanently stretched in being drawn from the supply roll. Many of the advantages of the present invention may also be enjoyed where the second feed rolls 57, 5S are, more or less, intermittently operated.

Having thus described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is:

l. A web feeding system comprising a supply roll of sheet material, means for rotatably mounting the supply roll, brake means for controlling rotation of the supply roll, a pair of feed rolls for drawing a web from said supply roll, loop forming means between said supply roll and said feed rolls, said loop forming means comprising irst and second slackener rolls, each movable to form loops of varying length, one of said slackener rolls exerting a weaker pull on the web than the other slackener roll, means for energizing said brake means when the length of loop around said one slackener roll exceeds a given minimum and de-energizing said brake means when the length of loop therearound reaches the speciiied minimum,

2. A web feeding system comprising a supply roll of polyethylene or like sheet material, means for rotatably mounting the supply roll, brake means for controlling rotation of the supply roll, intermittently operating feed rolls for drawing a web from said supply roll, loop forming means between said supply roll and said feed rolls, said loop forming means comprising first and second slackener rolls each movable to form loops of varying length, one of said slackener rolls exerting a weaker pull on the web than the other slackener roll, constant force spring means connected to the other of said slackener rolls and exerting a pull on said web approximating, but less than, the force required to permanently stretch the web, means for energizing said brake means when the length of loop around said one slacirener'roll exceeds a given minimum and deenergizing said brake means when the length of loop therearound reaches the specified minimum.

3. A web feeding system comprising a supply roll of sheet material, means for rotatably mounting the supply roll, brake means for controlling rotation of the supply roll, a pair of feed rolls for drawing a web from said supply roll, loop forming means between said supply roll and said feed rolls, said loop forming means comprising first and second slackener rolls, each movable in opposite directions to form two loops of varying length, said web being trained directly from one slackener roll to the other, one of said slackener rolls exerting a weaker pull on the web than the other slackener roll, means for energizing said brake means when the length of loop around the weaker slackener roll exceeds a given minimum and deenergizing said brake means when the length of loop therearound reaches the specified minimum.

4. A web feeding system comprising a supply roll of sheet material, means for rotatably mounting the supply roll, brake means for controlling rotation of the supply roll, feed roll means for feeding a web drawn from said supply roll, loop forming means between said feed roll means and said supply roll, said loop forming means cornprising first and second slackener rolls each movable to form two loops of varying length, one of said slackener rolls exerting a weaker pull on the web than the other slackener roll, means for energizing said brake means when the length of loop around said one slackener roll exceeds a given minimum and de-energizing said brake means when the length of loop around said one slackener roll reaches said given minimum, said feed roll means comprising a first and a second pair of feed rolls, means for forming a third loop in said web between said pairs of feed rolls, means for rotating said second pair of feed rolls, means for intermittently rotating said first pair of feed rolls at a rate of feed greater than that of the second pair of said rolls, and means responsive to the length of said third loop for actuating and stopping the rotating means for said first pair of feed rolls and maintaining the length of the third loop With the given limits.

5. A web feeding system eomprisi-ng a supply roll of polyethylene or like sheet material, means for rotatably mounting ithe supply troll, `brake means for controlling rotation oi the supply roll, feed roll means for advmoing a web drawn from said supply noli, loop yfonining means between said `feed roll means and said supply roll, said loop forming means comprising i'lnst and seoond slaekener rolls, each movable to `form loops oi" varying length, one of said slackener rolls exerting a weaker pull on the web than `the other slaokener roll, constant force spring means yoonneoteid to the other of said slaekener rolls lfor exerting a pull on said web which approximates but is less than the force which would permanently streteh the Weib, means yfor energizing said brake means when the length of the loop around said one slaiekener roll exceeds a given minimum `and deenergizing said brake means when the length of loop around said one slaickener noli reaches said given minimum, said feed roll means comprising a rst and a `second pair of ifeed rolls, means including a third sliaekener roll for iorming ya third loop in said web between said pairs of ieed rolls, said third slaekener roll maintaining a minimum pull on said weby sufficient to properly tnack it las itis advanced, means for rotating said second `pair `of feed rolls .at a constant rate, means for inenmittenitly rotating said first pair of `said rolls art a rate of feed greater than that toi the second pair of feed rolls, means `for preventing reverse rotar-tion of said rst pair of feed rolls and means responsive -to the length 'of said third loop for actuating and stopping the rotating means or said rst panof feed rolls to maintain the length of said third loop Within given limits.

6. rPhe method of feeding a polyethylene or like sheet matenial web from Ia rotatably mounted supply roll, wherein an intermittently operated pair of feed rolls draw the web from the supply roll and feed it to a cofnstantly rotating pan' of feed rolls, said method comprising the steps of forming rtwo loops in the `weby between the first named feed rolls and the supply roll, exenting a constunt `torce on one zo' said loops which approximates, but is less than, the torce which would permanently stretoh the web, exerting a weaker ioroe on the other of sai-d loops, controlling rotation oi the supp-ly roll in aecordance with the length of the other loop, forming a third loop in said web between the two pairs of feed rolls, exerting .a minimum pull on said third loop sucient to properly tnaek the web, and controlling operation of the intermittently operated feed Polls in response to the length of the third loop to maintain the length of said ythird loop within given limits.

7. A web feeding system wherein intermittently operating means are provided for drawing a webv from a supply roll of polyethylene or 4like sheet material, a suackener poll around which the web is trained between the supply roll and the dimming means, and guideways mounting the slaekener troll for movement to iorm a loop of varying length in said web, in `combination with constant force spring means connected to said slackener roll and urging it to term a loop of maximum length, the force of said spring means being related to the strength of the web in such proportion that the pull of the slankener roll on the web 'approximates but ldoes not exceed a pull which would permanently stretch the web, whereby a maximum permissible pull on the web will be available to `aocelerate the supply roll upon actuation of the drawing means.

References Cited in the le of this patent UNITED STATES PATENTS 1,941,597 Cavagna-ro Ian. 2, 1934 1,946,264 Baer Feb. 6, 1934 2,193,189 Brooke et al. Mair. 12, 1940 2,243,795 Eaddy May 2-7, 1941 2,343,181 Heinz Feb. 29, 1944 2,648,564 Ertner Aug. 11, 1953 2,737,089 Baumgartner Mair. 6, 1956 2,758,541 Tison Ang. l14, 1956 2,873,117 Croseld et al. Peb. 10, 1959 

7. A WEB FEEDING SYSTEM WHEREIN INTERMITTENTLY OPERATING MEANS ARE PROVIDED FOR DRAWING A WEB FROM A SUPPLY ROLL OF POLYETHYLENE OR LIKE SHEET MATERIAL, A SLACKENER ROLL AROUND WHICH THE WEB IS TRAINED BETWEEN THE SUPPLY ROLL AND THE DRAWING MEANS, AND GUIDEWAYS MOUNTING THE SLACKENER ROLL FOR MOVEMENT TO FORM A LOOP OF VARYING LENGTH IN SAID WEB, IN COMBINATION WITH CONSTANT FORCE SPRING MEANS CONNECTED TO SAID SLACKENER ROLL AND URGING IT TO FORM A LOOP OF MAXIMUM LENGTH, THE FORCE OF SAID SPRING MEANS BEING RELATED TO THE STRENGTH OF THE WEB IN SUCH PROPORTION THAT THE PULL OF THE SLACK- 